1. Field of the Invention
This invention relates to a magneto-optical recording medium used with a magneto-optical memory, a magnetic recording and display element or the like and capable of reading out information by the use of a magneto-optic effect such as magnetic Kerr effect or Faraday effect, and particularly to a magnetic thin film recording medium having improved corrosion resistance.
2. Description of the Prior Art
Polycrystal thin films such as MnBi and MnCuBi, amorphous thin films such as GdCo, GdFe, TbFe, DyFe, GdTbFe and TbDyFe, and single crystal thin films such as GdIG, etc. are known as magneto-optical recording mediums.
Of these thin films, the amorphous thin films have recently been considered to be excellent as magneto-optical recording mediums by taking into account of the film-making property with which a thin film of a large area is made at a temperature near the room temperature, the writing efficiency for writing signals by a little light-heat energy, the reading-out efficiency for reading out the written signals at a good S/N ratio, etc. Particularly, GdTbFe which has a great Kerr rotation angle and a curie point of about 150.degree. C. is best suited as a magneto-optical recording medium. Further, we have studied with a view to improve the Kerr rotation angle and as a result, have found that GdTbFeCo is a magneto-optical recording medium having a sufficiently great Kerr rotation angle and capable of reading out information at a good S/N ratio.
However, poor corrosion resistance may be mentioned as a characteristic of an amorphous magnetic material such as GdTbFe or GdTbFeCo. That is, when such material contacts the atmospheric air or water vapor, not only its magnetic characteristic is reduced but also finally it is completely oxidized and becomes transparent.
Therefore, there has heretofore been proposed a disc-like recording medium in which a protective layer is provided on the recording layer or in which the recording layer is enveloped by inert gas.